1. Field of the Invention
The present invention relates to a novel method of production of a plastic laminate comprising a protective layer on the surface of a foamed layer of a polyvinyl chloride, More particularly, the present invention relates to a method of efficiently producing a plastic laminate comprising a crosslinked protective layer of a polyvinyl chloride or a polyacrylate having excellent strength, abrasion resistance and resistance to chemicals of the surface on a foamed layer of polyvinyl chloride.
2. Description of the Prior Art
Foamed materials of polyvinyl chloride have excellent ability for design and flame retarding property and have heretofore been used as raw materials for building materials, such as wall materials and floor materials. As the wall papers and floorings, laminates having protective layer for protecting the surface of the foamed materials are frequently used.
For the formation of the protective layer on the surface of the foamed materials, materials and methods of processing are suitably selected depending on the purpose. For example, when durability, such as resistance to chemicals, strength and abrasion resistance, is enhanced, a method in which a polyvinyl chloride pastisol containing a vinyl chloride resin of high degree of polymerization, such as a resin having average degree of polymerization of 1600 or more, or a polyvinyl chloride plastisol containing crosslinking agent, such as triazine, is coated on the surface of the foamed material and then heated to form a protective layer and a method in which a polyvinyl chloride film by calender processing containing a plasticizer in a smaller amount, such as 35 weight parts per 100 weight parts of the vinyl chloride resin, is laminated are adopted.
In another method, emulsion or film of other than polyvinyl chloride, such as polyacrylate and the like, is laminated or coated.
Recently, prevention of fouling of wall papers and floorings are strongly desired because of change of style of living. Organic solvents are frequently used in household generally for cleaning fouled materials. When an organic solvent which dissolves polyvinyl chlorides is used for this purpose, the protective layer is reduced to be ineffective. By this reason, the method in which a crosslinked protective layer is formed by using a plastisol containing a crosslinking agent, such as triazine compounds and the like, has been adopted as the preferable method.
However, this method has drawbacks that the polyvinyl chloride tends to be thermally degraded during processing and that formed articles have inferior weatherability, tending to cause loss of transparency and whitening with humidity.
On the other hand, the method of using raw materials other than polyvinyl chloride, such as emulsions and films of polyacrylate, has drawbacks that it cannot exhibit the properties sufficiently and that cost of the product is increased.